Chart rendering code

HChartRender.hs

-- | This function bridges gi-cairo with the hand-written cairo
-- package. It takes a `GI.Cairo.Context` (as it appears in gi-cairo),
-- and a `Render` action (as in the cairo lib), and renders the
-- `Render` action into the given context.
renderWithContext :: GI.Cairo.Context -> ReaderT Cairo IO a -> IO (a)
renderWithContext ct rendered = withManagedPtr ct $ \p -> runReaderT rendered (Cairo (castPtr p))
activateRender :: (Int, Int) -> (Channel, DrawingArea) -> IO ()
activateRender (width, height) (channel, cairoArea) = do
  widgetSetSizeRequest cairoArea (fromIntegral width) (fromIntegral height)
  
  on cairoArea #draw $ \context -> do
    values <- readChannel channel
    let chartRendered = render (chart values) (fromIntegral width, fromIntegral height)
        asRender = runBackend (defaultEnv bitmapAlignmentFns) chartRendered
        !rendered = (runRender asRender)
        -- As far as i understand, "!rendered" 
    renderWithContext context rendered
    return True
  return ()
  
  chart :: [(Float, Float)] -> Renderable ()
chart xyTuples = toRenderable layout
  where
    fontsize = 16
    sinusoid2 = plot_points_style .~ filledCircles 1.5 (opaque blue)
              $ plot_points_values .~ xyTuples
              $ plot_points_title .~ "Magic"
              $ def

    layout = layout_title .~ "MagicLines"
             $ layout_plots .~ [toPlot sinusoid2]
             $ layout_x_axis . laxis_title .~ "Time"
             $ layout_y_axis . laxis_title .~ "Amplitude"
             $ layout_all_font_styles . font_size .~ fontsize
             $ def